Well, then Snowden should have simply kept doing what was legal, right?

After all, "I was just following orders" has always been a good answer, hasn't it?

Snowden feels that he has done nothing WRONG... huge difference between that and saying he did nothing ILLEGAL. He knows he broke the law (numerous laws actually) but he felt that it was his moral duty to expose wrongdoing. There are plenty of wrong actions that are legal and plenty of right actions that are illegal. Let's not confuse the two.